The invention relates to a device and a process for liquid treatment of a defined section of wafer-shaped article, a section near the edge, especially of a wafer.
The reason for treatment of a defined section of wafer-shaped article near the edge, especially of a wafer, will be described below.
A wafer, for example a silicon wafer, can for example have a silicon dioxide coating on all sides. For subsequent processes (if for example a layer of gold or a layer of polysilicon (polycrystalline silicon) is to be applied), it can be necessary to remove the existing coating from the wafer at least in the edge area of the main surface, but optionally also in the area of its peripheral surface and/or the second main surface. This is done by etching processes which can be divided mainly into dry etching processes and wet etching processes.
Another application is the cleaning of wafers. Here it can be necessary to clean a wafer at least in the edge area of a main surface, but optionally also in the area of its peripheral surface and/or the second main surface, i.e. to remove particles and/or other contamination. This is done by wet cleaning processes.
The invention is aimed at wet etching and wet cleaning (combined under the concept of liquid treatment). In doing so the surface area of the wafer to be treated is wetted with the treatment liquid and the layer which is to be removed or the impurities are carried off.
A device for executing this liquid treatment is described for example in U.S. Pat. No. 4,903,717. In this device the wafer-shaped article (wafer) is mounted on a spin chuck. The treatment liquid, for example, an etching liquid, is applied to the wafer surface to be treated, the liquid is distributed as a result of the rotational motion of the wafer over its surface and is flung off laterally over the edge of the wafer.
To prevent the treatment liquid from reaching the surface which is not be to treated in an uncontrolled manner, in U.S. Pat. No. 4,903,717 a chuck is proposed which flushes the surface which faces the chuck and which is not to be treated with a gas. In doing so the gas emerges between the wafer edge and the chuck.
JP 09-181026 A describes a chuck for semiconductor wafers which outside of an annular nozzle has a special shape, for example an annular step which falls away to the outside or a bevelling of its edge. In addition, a suction opening is proposed. This shaping of the intake opening is designed to influence (reduce) the flow velocity in the edge area. This is intended to serve such that the treatment liquid which has been applied from overhead flows beyond the edge of the wafer onto the side facing the chuck and treats the edge area there.
Regardless of whether a means to hold the wafer-shaped article (chuck) is used as claimed in U.S. Pat. No. 4,903,717 or JP 09-181026 A, an edge area of 1.5 mm (measured from the outer edge of the wafer) at most can be treated on the main surface facing the chuck. The liquid afterwards flows back in the direction of the wafer edge and is flung off by it.